FYI:
http://gmauthority.com/blog/gm/chevrolet/tahoe/2017-tahoe/
I'm guessing the 8 speed will become a reality cross platform with the 10 speed coming in soon after.
For me...the 6 speed is a big improvement over the 4 & 5 speed boxes it replaced. That being said and having driven 8 speed Escalades and Denali's I can only imagine how smooth the 10 speed will be.
In daily driving around town in traffic, the transmission improvements far exceed the benefits of a bit more power for my use. I have owned a 2004 Mercedes S500 for 11 years with the 7 speed Automatic. Having the extra gears to reach into coupled with variable cam timing puts you right on the sweet spot of the power curve at all times.
I'm looking forward to the 10 speed being paired with the 5.3 EcoTech as a VERY sweet package in the Tahoe/Yukon/Silverado/Sierra line up.